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Loose valve seats

Discussion in 'Mechanic and Repair' started by sdwally, Jul 10, 2001.

  1. sdwally

    sdwally LawnSite Senior Member
    Messages: 386

    I noticed in on of the posts that some engines(Onans) have loose valve seats when cold. You need to correct this problem soon before it causes worse problems.
    The fix is fairly simple. Remove the head and then with the valves in the closed position and the valve seats fully seated, use a center punch and stake the seats in place. Usually about 8 or more stakes per seat, depending on valve size. It is a good idea to lap the valves after doing this.
    If the valve seats float they will eventually erode the block and the the seats will never stay in place. B&S had this problem about 10 years ago when they accidentally assembled "green" blocks(not fully cured after casting). Also as the block wears from a floating valve seat your valve clearence will change.
  2. 75

    75 LawnSite Senior Member
    Messages: 992

    Thank you for this info Clay!

    One question: Is this a problem across the Onan line or is it specific to certain engine models? Just wondering about the P216's on our welding machines.
  3. sdwally

    sdwally LawnSite Senior Member
    Messages: 386

    As far as I know it is not a common problem in Onans, however I have run across the problem in various engine brands. Most of the time it is just a rare occasion that you'll find this problem.
    Some symtoms are the engine will stumble under a load or backfiring. Normally it is only the exhaust valve seat, however occasionally I have found loose intake seats.
    If you suspect this you can check it by removing the head when the engine is cold. If the problem is bad you will see the valve seat is not fully seated(protruding from the block). If fully seated, turn the engine over by hand until the valve is fully open and see if you can rotate the valve seat. If the valve seat will not rotate, then it is ok.
  4. 75

    75 LawnSite Senior Member
    Messages: 992

    Again, thank you for the info.

    None of our engines have been giving any trouble in the performance department, if they do now we know one thing to check & how to go about it.

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